For many years, it has been customary to position a burial vault in a grave and then place the casket within the burial vault. The vaults are sealed to prevent the entrance of air and water. In addition, the vaults should be structurally strong enough to support the weight of soil backfilled into the grave so that the vault, and not the casket, supports the weight of the soil.
To provide a vault having good structural integrity to support the weight of soil, vaults have been formed of a wide variety of materials. The construction of such vaults has included the use heavy wood, concrete, steel, and the like. Vaults formed of such materials can have adequate structural and tensile strength to resist the crushing force of the overlying earth load, as well as when it is subjected to the additional pressure of earth handling machinery moved thereover, as is common practice in cemetery operations. However, such vaults, particularly those formed of reinforced concrete, are heavy and can allow moisture to infiltrate through the porous concrete wall of the vault.
More recently synthetic materials such as fiberglass or plastics have been used to construct burial vaults. Such materials are impervious to air and water penetration. Vaults constructed entirely of synthetic materials, however, typically lack adequate structural, tensile and flexural strength and thus cannot withstand the crushing weight of the earth load and the weight of heavy equipment moved thereover.
Examples of prior attempts to provide a structurally sound and waterproof vault include U.S. Pat. No. 4,253,220 to Work. The Work patent discloses a molded plastic burial vault having a box and lid portions. Each of the box and lid portions include integrally formed ribs. The ribs are provided with corresponding tongue and groove portions that latch the box and lid together. In addition, the patent states that a pair of corresponding flanges having mutual tongue and grooves and a sealing compound placed therebetween to form a watertight seal.
U.S. Pat. No. 3,868,799 to Hayward discloses a burial vault having a cover and base portion which are held together by a plurality of lugs and notches to form a snaplock type latching mechanism. The vault includes integrally formed reinforcing ribs and a one-way seal that prohibits the passage of gasses and liquids into the vault while permitting the egress of gasses and liquids from the vault.
U.S. Pat. No. 4,315,353 discloses a plastic burial vault with a cover portion and a base portion. The cover portion has integrally formed ribs and is held to the base portion with threaded fasteners. A gasket between the cover and base seals the vault from the entrance of water.
Despite these and other burial vaults, it would be advantageous to provide a burial vault exhibiting improved structural strength and integrity. Further, it would advantageous to provide a burial vault which would optimize load transfer from the upper portion of the vault receiving the weight of backfilled soil to a lower portion thereof to prevent unnecessary and possibly debilitating pressure on fastening and sealing mechanisms thereof. It would be particularly desirable to provide such a structurally sound burial vault, which is also substantially air and water impervious and which can be easily and efficiently manufactured and assembled.